block: remove per-queue plugging
[linux-2.6.git] / drivers / s390 / char / tape_block.c
1 /*
2  *  drivers/s390/char/tape_block.c
3  *    block device frontend for tape device driver
4  *
5  *  S390 and zSeries version
6  *    Copyright (C) 2001,2003 IBM Deutschland Entwicklung GmbH, IBM Corporation
7  *    Author(s): Carsten Otte <cotte@de.ibm.com>
8  *               Tuan Ngo-Anh <ngoanh@de.ibm.com>
9  *               Martin Schwidefsky <schwidefsky@de.ibm.com>
10  *               Stefan Bader <shbader@de.ibm.com>
11  */
12
13 #define KMSG_COMPONENT "tape"
14 #define pr_fmt(fmt) KMSG_COMPONENT ": " fmt
15
16 #include <linux/fs.h>
17 #include <linux/module.h>
18 #include <linux/blkdev.h>
19 #include <linux/mutex.h>
20 #include <linux/interrupt.h>
21 #include <linux/buffer_head.h>
22 #include <linux/kernel.h>
23
24 #include <asm/debug.h>
25
26 #define TAPE_DBF_AREA   tape_core_dbf
27
28 #include "tape.h"
29
30 #define TAPEBLOCK_MAX_SEC       100
31 #define TAPEBLOCK_MIN_REQUEUE   3
32
33 /*
34  * 2003/11/25  Stefan Bader <shbader@de.ibm.com>
35  *
36  * In 2.5/2.6 the block device request function is very likely to be called
37  * with disabled interrupts (e.g. generic_unplug_device). So the driver can't
38  * just call any function that tries to allocate CCW requests from that con-
39  * text since it might sleep. There are two choices to work around this:
40  *      a) do not allocate with kmalloc but use its own memory pool
41  *      b) take requests from the queue outside that context, knowing that
42  *         allocation might sleep
43  */
44
45 /*
46  * file operation structure for tape block frontend
47  */
48 static DEFINE_MUTEX(tape_block_mutex);
49 static int tapeblock_open(struct block_device *, fmode_t);
50 static int tapeblock_release(struct gendisk *, fmode_t);
51 static int tapeblock_medium_changed(struct gendisk *);
52 static int tapeblock_revalidate_disk(struct gendisk *);
53
54 static const struct block_device_operations tapeblock_fops = {
55         .owner           = THIS_MODULE,
56         .open            = tapeblock_open,
57         .release         = tapeblock_release,
58         .media_changed   = tapeblock_medium_changed,
59         .revalidate_disk = tapeblock_revalidate_disk,
60 };
61
62 static int tapeblock_major = 0;
63
64 static void
65 tapeblock_trigger_requeue(struct tape_device *device)
66 {
67         /* Protect against rescheduling. */
68         if (atomic_cmpxchg(&device->blk_data.requeue_scheduled, 0, 1) != 0)
69                 return;
70         schedule_work(&device->blk_data.requeue_task);
71 }
72
73 /*
74  * Post finished request.
75  */
76 static void
77 __tapeblock_end_request(struct tape_request *ccw_req, void *data)
78 {
79         struct tape_device *device;
80         struct request *req;
81
82         DBF_LH(6, "__tapeblock_end_request()\n");
83
84         device = ccw_req->device;
85         req = (struct request *) data;
86         blk_end_request_all(req, (ccw_req->rc == 0) ? 0 : -EIO);
87         if (ccw_req->rc == 0)
88                 /* Update position. */
89                 device->blk_data.block_position =
90                   (blk_rq_pos(req) + blk_rq_sectors(req)) >> TAPEBLOCK_HSEC_S2B;
91         else
92                 /* We lost the position information due to an error. */
93                 device->blk_data.block_position = -1;
94         device->discipline->free_bread(ccw_req);
95         if (!list_empty(&device->req_queue) ||
96             blk_peek_request(device->blk_data.request_queue))
97                 tapeblock_trigger_requeue(device);
98 }
99
100 /*
101  * Feed the tape device CCW queue with requests supplied in a list.
102  */
103 static int
104 tapeblock_start_request(struct tape_device *device, struct request *req)
105 {
106         struct tape_request *   ccw_req;
107         int                     rc;
108
109         DBF_LH(6, "tapeblock_start_request(%p, %p)\n", device, req);
110
111         ccw_req = device->discipline->bread(device, req);
112         if (IS_ERR(ccw_req)) {
113                 DBF_EVENT(1, "TBLOCK: bread failed\n");
114                 blk_end_request_all(req, -EIO);
115                 return PTR_ERR(ccw_req);
116         }
117         ccw_req->callback = __tapeblock_end_request;
118         ccw_req->callback_data = (void *) req;
119         ccw_req->retries = TAPEBLOCK_RETRIES;
120
121         rc = tape_do_io_async(device, ccw_req);
122         if (rc) {
123                 /*
124                  * Start/enqueueing failed. No retries in
125                  * this case.
126                  */
127                 blk_end_request_all(req, -EIO);
128                 device->discipline->free_bread(ccw_req);
129         }
130
131         return rc;
132 }
133
134 /*
135  * Move requests from the block device request queue to the tape device ccw
136  * queue.
137  */
138 static void
139 tapeblock_requeue(struct work_struct *work) {
140         struct tape_blk_data *  blkdat;
141         struct tape_device *    device;
142         struct request_queue *  queue;
143         int                     nr_queued;
144         struct request *        req;
145         struct list_head *      l;
146         int                     rc;
147
148         blkdat = container_of(work, struct tape_blk_data, requeue_task);
149         device = blkdat->device;
150         if (!device)
151                 return;
152
153         spin_lock_irq(get_ccwdev_lock(device->cdev));
154         queue  = device->blk_data.request_queue;
155
156         /* Count number of requests on ccw queue. */
157         nr_queued = 0;
158         list_for_each(l, &device->req_queue)
159                 nr_queued++;
160         spin_unlock(get_ccwdev_lock(device->cdev));
161
162         spin_lock_irq(&device->blk_data.request_queue_lock);
163         while (
164                 blk_peek_request(queue) &&
165                 nr_queued < TAPEBLOCK_MIN_REQUEUE
166         ) {
167                 req = blk_fetch_request(queue);
168                 if (rq_data_dir(req) == WRITE) {
169                         DBF_EVENT(1, "TBLOCK: Rejecting write request\n");
170                         spin_unlock_irq(&device->blk_data.request_queue_lock);
171                         blk_end_request_all(req, -EIO);
172                         spin_lock_irq(&device->blk_data.request_queue_lock);
173                         continue;
174                 }
175                 nr_queued++;
176                 spin_unlock_irq(&device->blk_data.request_queue_lock);
177                 rc = tapeblock_start_request(device, req);
178                 spin_lock_irq(&device->blk_data.request_queue_lock);
179         }
180         spin_unlock_irq(&device->blk_data.request_queue_lock);
181         atomic_set(&device->blk_data.requeue_scheduled, 0);
182 }
183
184 /*
185  * Tape request queue function. Called from ll_rw_blk.c
186  */
187 static void
188 tapeblock_request_fn(struct request_queue *queue)
189 {
190         struct tape_device *device;
191
192         device = (struct tape_device *) queue->queuedata;
193         DBF_LH(6, "tapeblock_request_fn(device=%p)\n", device);
194         BUG_ON(device == NULL);
195         tapeblock_trigger_requeue(device);
196 }
197
198 /*
199  * This function is called for every new tapedevice
200  */
201 int
202 tapeblock_setup_device(struct tape_device * device)
203 {
204         struct tape_blk_data *  blkdat;
205         struct gendisk *        disk;
206         int                     rc;
207
208         blkdat = &device->blk_data;
209         blkdat->device = device;
210         spin_lock_init(&blkdat->request_queue_lock);
211         atomic_set(&blkdat->requeue_scheduled, 0);
212
213         blkdat->request_queue = blk_init_queue(
214                 tapeblock_request_fn,
215                 &blkdat->request_queue_lock
216         );
217         if (!blkdat->request_queue)
218                 return -ENOMEM;
219
220         rc = elevator_change(blkdat->request_queue, "noop");
221         if (rc)
222                 goto cleanup_queue;
223
224         blk_queue_logical_block_size(blkdat->request_queue, TAPEBLOCK_HSEC_SIZE);
225         blk_queue_max_hw_sectors(blkdat->request_queue, TAPEBLOCK_MAX_SEC);
226         blk_queue_max_segments(blkdat->request_queue, -1L);
227         blk_queue_max_segment_size(blkdat->request_queue, -1L);
228         blk_queue_segment_boundary(blkdat->request_queue, -1L);
229
230         disk = alloc_disk(1);
231         if (!disk) {
232                 rc = -ENOMEM;
233                 goto cleanup_queue;
234         }
235
236         disk->major = tapeblock_major;
237         disk->first_minor = device->first_minor;
238         disk->fops = &tapeblock_fops;
239         disk->private_data = tape_get_device(device);
240         disk->queue = blkdat->request_queue;
241         set_capacity(disk, 0);
242         sprintf(disk->disk_name, "btibm%d",
243                 device->first_minor / TAPE_MINORS_PER_DEV);
244
245         blkdat->disk = disk;
246         blkdat->medium_changed = 1;
247         blkdat->request_queue->queuedata = tape_get_device(device);
248
249         add_disk(disk);
250
251         tape_get_device(device);
252         INIT_WORK(&blkdat->requeue_task, tapeblock_requeue);
253
254         return 0;
255
256 cleanup_queue:
257         blk_cleanup_queue(blkdat->request_queue);
258         blkdat->request_queue = NULL;
259
260         return rc;
261 }
262
263 void
264 tapeblock_cleanup_device(struct tape_device *device)
265 {
266         flush_work_sync(&device->blk_data.requeue_task);
267         tape_put_device(device);
268
269         if (!device->blk_data.disk) {
270                 goto cleanup_queue;
271         }
272
273         del_gendisk(device->blk_data.disk);
274         device->blk_data.disk->private_data = NULL;
275         tape_put_device(device);
276         put_disk(device->blk_data.disk);
277
278         device->blk_data.disk = NULL;
279 cleanup_queue:
280         device->blk_data.request_queue->queuedata = NULL;
281         tape_put_device(device);
282
283         blk_cleanup_queue(device->blk_data.request_queue);
284         device->blk_data.request_queue = NULL;
285 }
286
287 /*
288  * Detect number of blocks of the tape.
289  * FIXME: can we extent this to detect the blocks size as well ?
290  */
291 static int
292 tapeblock_revalidate_disk(struct gendisk *disk)
293 {
294         struct tape_device *    device;
295         unsigned int            nr_of_blks;
296         int                     rc;
297
298         device = (struct tape_device *) disk->private_data;
299         BUG_ON(!device);
300
301         if (!device->blk_data.medium_changed)
302                 return 0;
303
304         rc = tape_mtop(device, MTFSFM, 1);
305         if (rc)
306                 return rc;
307
308         rc = tape_mtop(device, MTTELL, 1);
309         if (rc < 0)
310                 return rc;
311
312         pr_info("%s: Determining the size of the recorded area...\n",
313                 dev_name(&device->cdev->dev));
314         DBF_LH(3, "Image file ends at %d\n", rc);
315         nr_of_blks = rc;
316
317         /* This will fail for the first file. Catch the error by checking the
318          * position. */
319         tape_mtop(device, MTBSF, 1);
320
321         rc = tape_mtop(device, MTTELL, 1);
322         if (rc < 0)
323                 return rc;
324
325         if (rc > nr_of_blks)
326                 return -EINVAL;
327
328         DBF_LH(3, "Image file starts at %d\n", rc);
329         device->bof = rc;
330         nr_of_blks -= rc;
331
332         pr_info("%s: The size of the recorded area is %i blocks\n",
333                 dev_name(&device->cdev->dev), nr_of_blks);
334         set_capacity(device->blk_data.disk,
335                 nr_of_blks*(TAPEBLOCK_HSEC_SIZE/512));
336
337         device->blk_data.block_position = 0;
338         device->blk_data.medium_changed = 0;
339         return 0;
340 }
341
342 static int
343 tapeblock_medium_changed(struct gendisk *disk)
344 {
345         struct tape_device *device;
346
347         device = (struct tape_device *) disk->private_data;
348         DBF_LH(6, "tapeblock_medium_changed(%p) = %d\n",
349                 device, device->blk_data.medium_changed);
350
351         return device->blk_data.medium_changed;
352 }
353
354 /*
355  * Block frontend tape device open function.
356  */
357 static int
358 tapeblock_open(struct block_device *bdev, fmode_t mode)
359 {
360         struct gendisk *        disk = bdev->bd_disk;
361         struct tape_device *    device;
362         int                     rc;
363
364         mutex_lock(&tape_block_mutex);
365         device = tape_get_device(disk->private_data);
366
367         if (device->required_tapemarks) {
368                 DBF_EVENT(2, "TBLOCK: missing tapemarks\n");
369                 pr_warning("%s: Opening the tape failed because of missing "
370                            "end-of-file marks\n", dev_name(&device->cdev->dev));
371                 rc = -EPERM;
372                 goto put_device;
373         }
374
375         rc = tape_open(device);
376         if (rc)
377                 goto put_device;
378
379         rc = tapeblock_revalidate_disk(disk);
380         if (rc)
381                 goto release;
382
383         /*
384          * Note: The reference to <device> is hold until the release function
385          *       is called.
386          */
387         tape_state_set(device, TS_BLKUSE);
388         mutex_unlock(&tape_block_mutex);
389         return 0;
390
391 release:
392         tape_release(device);
393  put_device:
394         tape_put_device(device);
395         mutex_unlock(&tape_block_mutex);
396         return rc;
397 }
398
399 /*
400  * Block frontend tape device release function.
401  *
402  * Note: One reference to the tape device was made by the open function. So
403  *       we just get the pointer here and release the reference.
404  */
405 static int
406 tapeblock_release(struct gendisk *disk, fmode_t mode)
407 {
408         struct tape_device *device = disk->private_data;
409  
410         mutex_lock(&tape_block_mutex);
411         tape_state_set(device, TS_IN_USE);
412         tape_release(device);
413         tape_put_device(device);
414         mutex_unlock(&tape_block_mutex);
415
416         return 0;
417 }
418
419 /*
420  * Initialize block device frontend.
421  */
422 int
423 tapeblock_init(void)
424 {
425         int rc;
426
427         /* Register the tape major number to the kernel */
428         rc = register_blkdev(tapeblock_major, "tBLK");
429         if (rc < 0)
430                 return rc;
431
432         if (tapeblock_major == 0)
433                 tapeblock_major = rc;
434         return 0;
435 }
436
437 /*
438  * Deregister major for block device frontend
439  */
440 void
441 tapeblock_exit(void)
442 {
443         unregister_blkdev(tapeblock_major, "tBLK");
444 }